Organize tests utils

tests/termui/test_echo_via_pager.py

@@ -0,0 +1,191 @@
+import os
+import subprocess
+import sys
+from collections import namedtuple
+from contextlib import nullcontext
+from functools import partial
+from pathlib import Path
+from tempfile import tempdir
+from unittest.mock import patch
+
+import pytest
+
+import click
+from click import echo
+from click import echo_via_pager
+from click._compat import WIN
+
+
+def _test_gen_func():
+    yield "a"
+    yield "b"
+    yield "c"
+    yield "abc"
+
+
+def _test_gen_func_fails():
+    yield "test"
+    raise RuntimeError("This is a test.")
+
+
+def _test_gen_func_echo(file=None):
+    yield "test"
+    echo("hello", file=file)
+    yield "test"
+
+
+def _test_simulate_keyboard_interrupt(file=None):
+    yield "output_before_keyboard_interrupt"
+    raise KeyboardInterrupt()
+
+
+EchoViaPagerTest = namedtuple(
+    "EchoViaPagerTest",
+    (
+        "description",
+        "test_input",
+        "expected_pager",
+        "expected_stdout",
+        "expected_stderr",
+        "expected_error",
+    ),
+)
+
+
+@pytest.mark.skipif(WIN, reason="Different behavior on windows.")
+@pytest.mark.parametrize(
+    "pager_cmd", ["cat", "cat ", " cat ", "less", " less", " less "]
+)
+@pytest.mark.parametrize(
+    "test",
+    [
+        # We need to pass a parameter function instead of a plain param
+        # as pytest.mark.parametrize will reuse the parameters causing the
+        # generators to be used up so they will not yield anymore
+        EchoViaPagerTest(
+            description="Plain string argument",
+            test_input=lambda: "just text",
+            expected_pager="just text\n",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=None,
+        ),
+        EchoViaPagerTest(
+            description="Iterable argument",
+            test_input=lambda: ["itera", "ble"],
+            expected_pager="iterable\n",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=None,
+        ),
+        EchoViaPagerTest(
+            description="Generator function argument",
+            test_input=lambda: _test_gen_func,
+            expected_pager="abcabc\n",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=None,
+        ),
+        EchoViaPagerTest(
+            description="String generator argument",
+            test_input=lambda: _test_gen_func(),
+            expected_pager="abcabc\n",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=None,
+        ),
+        EchoViaPagerTest(
+            description="Number generator expression argument",
+            test_input=lambda: (c for c in range(6)),
+            expected_pager="012345\n",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=None,
+        ),
+        EchoViaPagerTest(
+            description="Exception in generator function argument",
+            test_input=lambda: _test_gen_func_fails,
+            # Because generator throws early on, the pager did not have
+            # a chance yet to write the file.
+            expected_pager="",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=RuntimeError,
+        ),
+        EchoViaPagerTest(
+            description="Exception in generator argument",
+            test_input=lambda: _test_gen_func_fails,
+            # Because generator throws early on, the pager did not have a
+            # chance yet to write the file.
+            expected_pager="",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=RuntimeError,
+        ),
+        EchoViaPagerTest(
+            description="Keyboard interrupt should not terminate the pager",
+            test_input=lambda: _test_simulate_keyboard_interrupt(),
+            # Due to the keyboard interrupt during pager execution, click program
+            # should abort, but the pager should stay open.
+            # This allows users to cancel the program and search in the pager
+            # output, before they decide to terminate the pager.
+            expected_pager="output_before_keyboard_interrupt",
+            expected_stdout="",
+            expected_stderr="",
+            expected_error=KeyboardInterrupt,
+        ),
+        EchoViaPagerTest(
+            description="Writing to stdout during generator execution",
+            test_input=lambda: _test_gen_func_echo(),
+            expected_pager="testtest\n",
+            expected_stdout="hello\n",
+            expected_stderr="",
+            expected_error=None,
+        ),
+        EchoViaPagerTest(
+            description="Writing to stderr during generator execution",
+            test_input=lambda: _test_gen_func_echo(file=sys.stderr),
+            expected_pager="testtest\n",
+            expected_stdout="",
+            expected_stderr="hello\n",
+            expected_error=None,
+        ),
+    ],
+)
+def test_echo_via_pager(monkeypatch, capfd, pager_cmd, test):
+    monkeypatch.setitem(os.environ, "PAGER", pager_cmd)
+    monkeypatch.setattr(click._termui_impl, "isatty", lambda x: True)
+
+    test_input = test.test_input()
+    expected_pager = test.expected_pager
+    expected_stdout = test.expected_stdout
+    expected_stderr = test.expected_stderr
+    expected_error = test.expected_error
+
+    check_raise = pytest.raises(expected_error) if expected_error else nullcontext()
+
+    pager_out_tmp = Path(tempdir) / "pager_out.txt"
+    pager_out_tmp.unlink(missing_ok=True)
+    with pager_out_tmp.open("w") as f:
+        force_subprocess_stdout = patch.object(
+            subprocess,
+            "Popen",
+            partial(subprocess.Popen, stdout=f),
+        )
+        with force_subprocess_stdout:
+            with check_raise:
+                echo_via_pager(test_input)
+
+    out, err = capfd.readouterr()
+
+    pager = pager_out_tmp.read_text()
+
+    assert pager == expected_pager, (
+        f"Unexpected pager output in test case '{test.description}'"
+    )
+    assert out == expected_stdout, (
+        f"Unexpected stdout in test case '{test.description}'"
+    )
+    assert err == expected_stderr, (
+        f"Unexpected stderr in test case '{test.description}'"
+    )